>Maybe use at least -O2 ? no difference. > You may want to try _mm_shuffle_pd or __builtin_shuffle. indeed, this reduces the runtime by 2 s. Still 3x slower than iter1. >Did you take a look at the generated code (use flag -S and read the >generated t.s)? Going back and forth between packed and unpacked through a >union often generates plenty of mov instructions. If you manually use >_mm_cvtsd_f64 and _mm_unpackhi_pd you may be able to save a bit. Note that >with the latest gcc, you can use the [] notation directly on your __m128d. yes, there are lots of move-instructions. It seems this adds a lot of runtime. > I'd be surprised if you managed any gain on this thanks to __m128d. well, maybe SIMD isn't very well suited for these calculations. So, I'll use iter1 until I have a better idea. thanks for your hints! -Boris -- View this message in context: http://old.nabble.com/SSE-SIMD-enhanced-code-4x-slower-than-regular-code-tp33159404p33161396.html Sent from the gcc - Help mailing list archive at Nabble.com.
